This invention relates to a fastener system, fastener system article such as a bolt, and a method of retaining a loose elongate fastener in a counterbore. In many industrial applications large bolts are used to releasably connect machinery parts together. The bolts may be deliberately positioned in holes that are oversized in relation to the diameter of the bolt shank, and with a counterbore that is oversized in relation to the size of the bolt head. This may be done for a number of reasons that include the desire to prevent impact shock applied directly to the bolt through the machine part, to allow easy bolt removal when desired, and to facilitate minute degrees of adjustment to the machine parts before the nut is tightened. In many such cases the counterbore is oversized to a sufficient degree to allow easy removal of the bolt, but is small enough to prevent more than a minimal degree of rotation. For example, with a hex-head bolt positioned in an oversized hex-shaped counterbore, the bolt may be allowed to rotate between 5-25 degrees, but not enough to allow a corner of the bolt head to pass a corner of the counterbore. This is desirable in order to permit the nut to be applied to and removed from the bolt without capturing the head with a wrench or similar tool to prevent rotation.
When repair, adjustment or replacement is required, the nut is removed from the bolt in order to separate the connected parts. When the bolt is captured and retained in the bolt hole by the nut instead of by mating threads on the bolt and the interior of the bolt hole, the bolt is susceptible to inadvertently exiting the bolt hole, either by an impact on the shank along the axis of the bolt, or by the bolt failing out of the bolt hole when the part is inverted. In such cases, the failing bolt may strike and injure a nearby worker, damage nearby machinery or be itself damaged.
As noted above, these fasteners are often recessed in counterbores. A “counterbore” can refer to a cylindrical flat-bottomed hole which enlarges another hole such as a through or blind bolt hole, or the tool used to create that feature. The term is usually used when a bolt or cap head screw is required to sit flush with or below the level of a workpiece or machine part surface. By comparison, a countersink refers to a conical hole used to seat a flathead screw. A very shallow counterbore, such as one machined on a cast part to provide a flat surface for a fastener head, may also be called a “spotface.” For purposes of this application, the term “counterbore” is used in a generic sense to refer to all of these specific structures, in order to avoid repetition and frequent use of alternative terms.
Therefore, there exists a need for a simple, effective and inexpensive way of retaining a bolt or similar fastener in a bolt hole that includes a counterbore, when the bolt or similar fastener is loosely positioned in the hole and not retained by a nut or similar element.
It is an object of the invention to provide a simple, effective and inexpensive way of retaining a bolt or similar fastener in a bolt hole.
These and other objects and advantages of the invention are achieved by providing a fastener system for retaining a loose elongate fastener in a counterbore, comprising an elongate fastener having a head for being received and retained in a counterbore in a structure and in generally flush relation to a surface of the structure surrounding the counterbore, and a retaining member for being secured to the structure proximate the counterbore and overlapping the counterbore to trap the loose fastener in the counterbore.
According to another embodiment of the invention, the head of the elongate fastener is polygonal and the counterbore is sized to permit limited rotation of the head.
According to yet another embodiment of the invention, the head of the fastener defines a first recess therein communicating with an edge thereof. A second recess is formed in the structure and communicates with the counterbore for being aligned with the first recess. The retaining member is adapted for being positioned in the aligned first and second recesses to trap the loose fastener in the counterbore.
According to yet another embodiment of the invention, the fastener comprises a bolt having an enlarged polygonal head and a threadless shank portion extending from the head and a threaded shank portion distal from the head.
According to yet another embodiment of the invention, the retaining member is retained in the recess by a screw threaded into a hole in the structure within the recess.
According to yet another embodiment of the invention, the retaining member substantially covers the counterbore.
According to yet another embodiment of the invention, the retaining member is retained in position over the counterbore by at least one screw extending through the retaining member and secured to the structure within the counterbore.
According to yet another embodiment of the invention, the retaining member comprises a bar extending across the counterbore and fastened to the structure on generally opposing sides thereof.
According to yet another embodiment of the invention, the retaining member comprises a bar extending across the counterbore and fastened to the structure on generally opposing sides thereof, and an inwardly-extending portion for engaging the head to prevent rotation thereof in the counterbore.
According to yet another embodiment of the invention, a fastener system is provided for retaining a loose elongate fastener in a counterbore, and comprises a bolt having a polygonal head for being received and retained in a counterbore in a structure and in generally flush relation to a surface of the structure surrounding the counterbore. The head of the bolt defines a first recess therein for communicating with an edge thereof, and a second recess formed in the structure and communicating with the counterbore for being aligned with the first recess. A retaining member is adapted for being positioned in the aligned first and second recesses to trap the loose bolt in the counterbore.
According to yet another embodiment of the invention, a method of retaining a loose elongate fastener in a counterbore is provided, and comprises the steps of providing an elongate fastener having a head for being received and retained in a counterbore in a structure in generally flush relation to a surface of the structure surrounding the counterbore, and a retaining member for being secured to the structure proximate the counterbore and overlapping the counterbore to trap the loose fastener in the counterbore. The fastener is positioned in the counterbore and the retaining member is positioned in overlapping relation to the head of the fastener. The retaining member is secured to the structure.
According to yet another embodiment of the invention, the method includes the steps of providing a first recess in the head of the fastener and communicating with an edge thereof, and a second recess formed in the structure and communicating with the counterbore for being aligned with the first recess.
According to yet another embodiment of the invention, the method includes the step of positioning the retaining member in the aligned first and second recesses to trap the loose fastener in the counterbore.
According to yet another embodiment of the invention, the method includes the step of retaining the retaining member in the recess by a screw threaded into a hole in the structure within the recess.
According to yet another embodiment of the invention, the method includes the step of substantially covering the counterbore with the retaining member.
According to yet another embodiment of the invention, the method includes the step of retaining the retaining member in position over the counterbore by at least one screw extending through the retaining member and secured to the structure within the counterbore.
According to yet another embodiment of the invention, the method includes the step of retaining the retaining member comprises the steps of positioning a bar across the counterbore and fastening the bar to the structure on generally opposing sides of the counterbore.
According to yet another embodiment of the invention, wherein the step of retaining the retaining member includes the steps of positioning a bar having an inwardly-extending portion for engaging the head to prevent rotation thereof in the counterbore across the counterbore, and fastening the bar to the structure on generally opposing sides.